/*

* Block Cipher Cascade

* (C) 2010 Jack Lloyd

*

* Botan is released under the Simplified BSD License (see license.txt)

*/

#include <botan/cascade.h>

namespace Botan {

void Cascade_Cipher::encrypt_n(const uint8_t in[], uint8_t out[],

                               size_t blocks) const

   {

   size_t c1_blocks = blocks * (block_size() / m_cipher1->block_size());

   size_t c2_blocks = blocks * (block_size() / m_cipher2->block_size());

   m_cipher1->encrypt_n(in, out, c1_blocks);

   m_cipher2->encrypt_n(out, out, c2_blocks);

   }

void Cascade_Cipher::decrypt_n(const uint8_t in[], uint8_t out[],

                               size_t blocks) const

   {

   size_t c1_blocks = blocks * (block_size() / m_cipher1->block_size());

   size_t c2_blocks = blocks * (block_size() / m_cipher2->block_size());

   m_cipher2->decrypt_n(in, out, c2_blocks);

   m_cipher1->decrypt_n(out, out, c1_blocks);

   }

void Cascade_Cipher::key_schedule(const uint8_t key[], size_t)

   {

   const uint8_t* key2 = key + m_cipher1->maximum_keylength();

   m_cipher1->set_key(key , m_cipher1->maximum_keylength());

   m_cipher2->set_key(key2, m_cipher2->maximum_keylength());

   }

void Cascade_Cipher::clear()

   {

   m_cipher1->clear();

   m_cipher2->clear();

   }

std::string Cascade_Cipher::name() const

   {

   return "Cascade(" + m_cipher1->name() + "," + m_cipher2->name() + ")";

   }

BlockCipher* Cascade_Cipher::clone() const

   {

   return new Cascade_Cipher(m_cipher1->clone(),

                             m_cipher2->clone());

   }

namespace {

size_t euclids_algorithm(size_t a, size_t b)

   {

   while(b != 0)

      {

      size_t t = b;

      b = a % b;

      a = t;

      }

   return a;

   }

size_t block_size_for_cascade(size_t bs, size_t bs2)

   {

   if(bs == bs2)

      return bs;

   const size_t gcd = euclids_algorithm(bs, bs2);

   return (bs * bs2) / gcd;

   }

}

Cascade_Cipher::Cascade_Cipher(BlockCipher* c1, BlockCipher* c2) :

   m_cipher1(c1), m_cipher2(c2)

   {

   m_block = block_size_for_cascade(c1->block_size(), c2->block_size());

   BOTAN_ASSERT(m_block % c1->block_size() == 0 &&

                m_block % c2->block_size() == 0,

                "Combined block size is a multiple of each ciphers block");

   }

}